How do I subdivide a cube?
For subdividing a cube non-uniformly: your best bet is using the Loopcut Tool ⌃ Ctrl + R in edit mode and then Scroll to add more segments). Some of blender's primitives don't have the options you want like other software does.
To add flat divisions uniformly: when in edit mode, press A to select all components and then RMB &gt;Subdivide (destructive operation, can no longer edit after activating a different tool). As long as you don't perform any operations afterwards, you can expand the little properties panel in the bottom left to control how many subdivisions you want.
For non-destructive smooth subdivision levels:
⌃ Ctrl + 1 for SubD level 1 ⌃ Ctrl + 2 for SubD level 2, etc. Using this hotkey simply adds a subdivision surface modifier and pressing different hotkeys for different levels simply changes the level of that exact same modifier. You can access this modifier from the Modifiers Panel on the right (little wrench).
For selecting ring of faces: Switch to Edit, then Face mode. ⌥ Alt + LMB  in between two faces to determine the direction of the loop. Add Shift to select more face rings or deselect existing ones.